The present invention relates to a tandem axle leaf spring suspension assembly for vehicles and more particularly to a tandem axle leaf spring vehicle suspension of the so-called 4-spring short-rocker tandem suspension type, among systems for the suspension of the two rear axles of a vehicle wherein each of the axles is provided with a pair of semielliptic leaf springs, one disposed on each side of the vehicle, and an equalizer is arranged on each side of the vehicle between the longitudinally arranged leaf springs to equalize the loadings of the two rear axles.
In general, two types have been known with regard to 4-spring short-rocker type tandem suspension assemblies, namely, one in which shackles are used to connect the equalizers to one end of each of the leaf springs as disclosed in, e.g., U.S. Pat. No. 4,033,606, and another in which the equalizers and one end of each of the leaf springs are arranged so as to be in a direct sliding contact relationship, without the use of shackles, as disclosed in e.g., U.S. Pat. No. 3,841,652. In comparing these, although the first type is able to provide excellent equalizing efficiency, it suffers from such defects as higher cost due to the greater number of parts, a greater amount of maintenance owing to the larger number of swivel joint support portions, difficulties in construction, and so on. Contrarily, although the second type is simple in terms of its construction, it involves such problems as that there is little freedom for the selection or improvement of the equalizing characteristics, and the equalizing characteristics may be insufficient. The latter type has, however, been widely used heretofore by reason of its relatively low cost.
The present invention belongs broadly to the second above-described type of 4-spring short-rocker tandem suspension assembly.